|Great Lakes System
Increased precipitation and lower temperatures during the Pleistocene epoch 500,000 years ago resulted in the glaciation of North America. The accumulation of glacial snow and ice over thousands of years caused the earth to sink and form vast depressions which carved out the Great Lakes as the glaciers receded. The lakes and rivers underwent numerous changes in shape and flow as the system developed its present-day contours.
Humans arrived in the Great Lakes area 14,000 years ago and began a long history of exploiting the natural resources. The waterways were used as transportation routes to hunt and gather food. Early inhabitants mined the area's vast supply of copper for use in weapons and jewelry.
Today, fresh water ranks first among the system's resources. The United States and Canada work together under the Boundary Waters Treaty of 1909 and the Great Lakes Water Quality Agreement of 1978 to remedy pollution and other natural resource problems facing the area. Nevertheless, the Great Lakes continue to suffer from overfishing, water and air pollution, and increased recreational use.
Ashworth, William. The Late, Great Lakes: An Environmental History. 1988.
Rousmaniere, John, ed. The Enduring Great Lakes. 1980.
U.S. Environmental Protection Agency and Government of Canada. The Great Lakes: An Environmental Atlas and Resource Book. 1995.
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